Diable Jambe is one of the signature techniques used by Sanji, talented cook and deadly combatant of Straw Hat Pirates in the manga and anime series One Piece. This powerful ability—literally "Devil Leg" in French—permits Sanji to heat his leg, which then adds extreme heated energy to the impact of his kicks. The technique was first revealed during the Enies Lobby arc, and it was a huge power-up for Sanji. This paralleled Zoro's Asura technique, also first shown in that storyline.
What definitely sets Diable Jambe apart from most other abilities in the One Piece universe is simply that, without a Devil Fruit, Sanji can create and manipulate fire. This characteristic has highly influenced fan discussion and theorizing over what the technique really is and where it originally came from. Some think it is the result of Sanji's passionate and strong will literally burning into flame, while others believe it is a case of extremely high friction caused by the rapid spinning motion of his body.
Activation typically involves spinning quickly on one leg, which builds up enough frictional heat to set the leg on fire. After he has set himself on fire, his kicks are imbued with very high heat that is potent enough to scorch his opponents and deal damage far greater than normal attacks. The visuals of the flaming Sanji's leg in the anime adaptation make Diable Jambe very recognizable and visually striking among all techniques in the series.
With the series' development of Sanji's skill, Diable Jambe has definitely been included. He has, in later arcs, such as Whole Cake Island and Wano, managed to enter it much faster and hold a bit longer. This shows not only the growth of Sanji as a warrior but also the message brought across by the series itself about character development and continuous improvement.
Sanji has developed different strong attacks that incorporated Diable Jambe. Notably among these are the Flambage Shot, a fight-ender kick that sends opponents flying, complemented by flames; Poêle à Frire: Spectre, a fast series of flaming kicks resembling a burning fan; and Hell Memories, where Sanji uses his painful memories to further increase the flame's intensity; it is one of Sanji's strongest attacks. These diverse applications of Diable Jambe highlight Sanji's resourcefulness and adaptability in fight situations.
The real significance of Diable Jambe lies outside its actual combat application. It is a metaphorical representation of Sanji's passion, which was initially cooking and later fighting. The name and appearance of the technique, full of vocabulary and motifs associated with cooking, further underline what makes Sanji unique among the Straw Hats: he is both an extraordinary chef and a legendary warrior. This mix of culinary expertise and martial prowess defines Sanji's character and separates him from other fighters in the world of One Piece.
Due to the popularity of this technique, it earned a spot on many One Piece–related media and merchandise. For example, the Figuarts ZERO line of collectible figures has a Sanji figure that makes a pose representing Diable Jambe. A fan can have in their hands an actual representation of this really iconic ability. The merchandise represents the status that the technique holds as one of the most recognizable and beloved parts of Sanji's character.
The technique of Diable Jambe shall continuously develop as the saga of One Piece goes on. By the end of each arc, fans will have noticed that Sanji is becoming increasingly powerful with this ability, leaving everyone in anticipation of what new variations or applications of his fiery kicks will emerge. The fact that Diable Jambe keeps evolving testifies to the great creativity Eiichiro Oda has embedded in One Piece and in character development in general.